Question

If you chew on a piece of bread long enough, it will begin to taste sweet because (a) maltase is breaking down maltose (b) lipases are forming fatty acids (c) amylase is breaking down starches to disaccharides (d) disaccharides are forming glucose.

Short answer

(c) Amylase is breaking down starches to disaccharides, leading to the sweet taste.

Step-by-step solution

Understand the process of digestion of bread

Recognize that bread is primarily composed of carbohydrates, which include starches. The process of digestion begins in the mouth where enzymes start breaking down these starches.

Identify the enzyme present in the mouth

Understand that the saliva in the mouth contains an enzyme called amylase. This enzyme is responsible for breaking down starches into simpler sugars.

Determine the cause of the sweetness

Recognize that as amylase breaks down the starches into simpler sugars, these sugars can begin to taste sweet. The sweetness is not due to maltase activity, lipases, or disaccharides directly forming glucose.

Connect the sweetness to the correct answer

Conclude that the sweet taste comes from the action of amylase converting starches into disaccharides, such as maltose, which are sweet. Hence, amylase is the enzyme related to the sweet taste when bread is chewed for a long time.

Key concepts

Salivary Amylase

Imagine taking the first bite of a soft, warm piece of bread. As you begin to chew, a process that might seem as simple as grinding food is actually the starting point of a sophisticated biological procedure - digestion. At the forefront of this process is a remarkable enzyme known as salivary amylase.

Salivary amylase is secreted by the salivary glands and makes its way into your mouth. Its main role is to kickstart the digestion of starches, which are complex carbs. Starches are too large for your body to absorb directly, so they must first be broken down into smaller, more manageable sugars. Salivary amylase clings onto starch molecules and begins to slice them apart, converting these larger molecules into maltose, a type of disaccharide which is composed of two glucose units.

Starch Breakdown

Starches are a staple in many diets, found abundantly in foods like bread, potatoes, and rice. They're composed of long chains of glucose molecules linked together. Your body is equipped with the tools to dismantle these chains because the individual glucose units are valuable sources of energy.

When starch enters your mouth, salivary amylase doesn't waste time; it targets the bonds that link glucose units together. The activity of this enzyme turns these long, insoluble glucose chains into shorter, water-soluble maltose molecules. This conversion is critical because it allows for these smaller sugars to be dissolved in the watery environment of your gut, facilitating further digestion down the line. Without this initial breakdown by salivary amylase, the starches would remain too large and complex for your body to make use of their bountiful energy.

Enzyme Activity in Digestion

Enzymes like salivary amylase are the unsung heroes of digestion. They're highly specific biological catalysts, speeding up chemical reactions in the body without being consumed in the process. As with all enzymes, salivary amylase has a particular type of molecule it interacts with, known as a substrate.

In the case of salivary amylase, its substrate is starch. Our body temperature provides the perfect warm environment for salivary amylase to thrive and quickly chop up those starch molecules. The efficiency of these enzymes is essential for digestion to occur within a reasonable time frame and is the reason why foods begin to taste sweet shortly after chewing, as they break down complex sugars into simpler, sweet-tasting ones. Enzyme activity in digestion is a precisely timed dance that ensures our bodies get nutrients in the right form at the right time.

Disaccharides

Common examples of disaccharides you might know are sucrose, lactose, and maltose. From a chemical standpoint, they are akin to a middle ground between the complex starches and the simple monosaccharides like glucose and fructose.

When salivary amylase breaks starch into maltose, it's simplifying a complex structure into something more palatable and manageable for the body to handle. Each maltose molecule still needs to be broken down further to yield two absorbable glucose molecules, but having these disaccharides is a significant step toward full digestion. This conversion is not only crucial for proper nutrient absorption but also explains the sweet taste you might notice when chewing bread for a prolonged period, as maltose is quite sweet to the taste buds.